Which UPS?

Scott Allen mlxxxp-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
Tue Jun 12 18:16:33 UTC 2012


On 12 June 2012 11:59, James Knott <james.knott-bJEeYj9oJeDQT0dZR+AlfA at public.gmane.org> wrote:
> Whether AC or DC supply to the power supply, there are two stages involved,
> conversion of AC to DC and then converting that DC to the required voltages
> through a switching converter/regulator.  I'd have to question why having
> both in the same package results in higher efficiencies of the order you
> claim.

I showed some math backing my claim, but I had to estimate the
efficiency of converting 120VAC to 48VDC in the UPS (and I think I was
quite liberal at 85%). Show me the math that would have you question
my claim.

> Many "server farms" run on about 200V DC or so and get better
> efficiencies than AC powered systems.  The rectified DC inside a typical
> power supply would be in the range approaching 170V.  The conversion of the
> high voltage DC to the voltages required by the computer should have about
> the same efficiency, no matter what the source, all else being equal.

How is that 200VDC produced? Is it regulated? Just rectifying AC is
quite efficient. It's chopping and changing to different voltages and
regulating that costs efficiency. Also, multiple conversions cost
efficiency.

-- 
Scott
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